<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .container{
            width: 200px;
            height: 200px;
            border: orangered 1px solid;
            box-shadow: -10px -10px 20px blue;

            /* 
            10px 横向阴影的尺寸 
            10px 纵向阴影的尺寸 
            20px 阴影模糊的距离 
            greeny阴影模糊的颜色 
            inset 阴影的位置  默认阴影位置是outset
             */
            
        }
    </style>
</head>
<body>
    <div class="container">

    </div>
</body>
</html>